Hi,
I'm doing a bit of research into mobility models and I'm currently exploring
implementation language choices for the simulator (yes, sadly it needs to be
a custom one).
I've been using Haskell here and there for some small tasks, and thought I
should consider it as an implementation language for the simulator.
While I already have an working implementation in Haskell, there is one thing
that I would like to express in a more elegant way, but just can't figure
out. The simulation algorithm requires expressing the node's mobility so that
it is "stateless". The mobility model algorithm's type should be something
like:
mobility_model :: WorldState -> NodeState -> OtherInput -> (Action, NodeState)
where Action can alter WorldState and the second NodeState is an altered input
NodeState. I perform a form of speculative execution on mobility_model so
sometimes I need to backtrack to a previous world and node state.
This is all fairly simple stuff, and was just an introduction. What I do now
is store an enum in NodeState and implement mobility_model as one big case
statement. Yes, this is very imperative of me, I know. What I'd like to do is
to express mobility_model, so that the code would look like:
mobility_model world node input = do
do_calculus
emit_action
if something
then emit_action
else emit_action
do_calculus
emit_action
mobility_model world node input
but I'd like to be able to alter world and node state before continuing from
emit_action.
I've tried to get this working by using the idea from
http://www.haskell.org/pipermail/haskell/2005-April/015684.html but couldn't
get the state-altering behavior I was looking for. I've also taken a look at
http://monadicheadaches.blogspot.com/2008/01/python-25s-iterators-in-haskell-sort-of.html,
the unified concurrency model and Control.Coroutine, but couldn't get the
behavior I was going for.
Thanks!
Marcin Kosiba
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